Amino Acid Metabolism and the Biosynthesis of Prothrombin in the Perfused Rat Liver 1

Abstract

Summary

The amino acid composition of the perfusate of an isolated rat liver varies markedly, and highly individually for given amino acids, over a 6-hr period. Glutamic acid, valine, isoleucine, and leucine concentrations increased whereas the concentrations of aspartic acid, proline, glycine, alanine, methionine, phenylalanine, lysine, and arginine decreased. In livers bathed in warfarin (10 μg/ml), vitamin K₁ added at 2 hr in a concentration of 25 μg/ml caused a prompt and linear increase in prothrombin. The specific activity of L-leucine-1-¹⁴C added to the perfusate at zero time declined exponentially to 4% of initial values as the concentration of total leucine increased 5-fold. The prothrombin synthesized under these conditions was highly radioactive, suggesting that vitamin K stimulates de novo synthesis of this coagulation protein.

The authors wish to thank Miss Lourdes Maglasang and Miss Katherine Compagno for able technical assistance.